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Powder residue on the rims, but not on the case necks? What primer are you using? I've been working with another Finn M39 shooter having sooty case problems (with Lapua D166's over 40 gr VV N140) and solved his problem when he followed my recommendation to switch to CCI 200 primers.
 

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Discussion Starter · #3 ·
Powder residue on the rims, but not on the case necks? What primer are you using? I've been working with another Finn M39 shooter having sooty case problems (with Lapua D166's over 40 gr VV N140) and solved his problem when he followed my recommendation to switch to CCI 200 primers.
leon,
already using cci 200 primers. yeah, I got soot on the necks too. pretty much all of the necks have soot, but some more than others. some have smudges on the side, about mid case. not many, like the dirty rims, but some. I measured the fired cases, and they're coming out at 2.080 or thereabouts.
 

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leon,
already using cci 200 primers. yeah, I got soot on the necks too. pretty much all of the necks have soot, but some more than others. some have smudges on the side, about mid case. not many, like the dirty rims, but some. I measured the fired cases, and they're coming out at 2.080 or thereabouts.
Get the Lee factory crimp die and try crimping the case neck. The D166 has a crimp cannelure.

I am assuming you are loading for a Finn M39. One of the major problems encountered with reloading 7.62X53R is getting the correct expander button. The D166 has a nominal diameter of .3095, so you need an expander that is 0.001"~0.0015" smaller in order to get proper neck tension. I use Forster dies, and obtained a .3085" expander button from them for my die. Forster sells these for loaders that "soft seat" their bullets.
 

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Discussion Starter · #5 ·
Get the Lee factory crimp die and try crimping the case neck. The D166 has a crimp cannelure.

I am assuming you are loading for a Finn M39. One of the major problems encountered with reloading 7.62X53R is getting the correct expander button. The D166 has a nominal diameter of .3095, so you need an expander that is 0.010"~0.015" smaller in order to get proper neck tension. I use Forster dies, and obtained a .3085" expander button from them for my die. Forster sells these for loaders that "soft seat" their bullets.
I will do those. thanks
 

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The standard Finnish service round for the M39 is the 200 gr Lapua D166 over 40 gr N140. Forty grains is far from full case fill - high charge density - which typically is what reloaders strive for. A full case is basically self tamping. For this reason neck tension is particularly critical when loading. The primer will generate enough pressure to start the bullet on its way before case pressure rises sufficiently to initiate complete powder ignition. This is why I suggest crimping, although that is merely a crutch for inconsistent or inadequate case neck tension.

Some folk recommend using "hotter" primers, like the Winchester RL, or even magnum primers. These may work, but as I pointed out, they are only a crutch, not a solution.
 

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Discussion Starter · #8 ·
The standard Finnish service round for the M39 is the 200 gr Lapua D166 over 40 gr N140. Forty grains is far from full case fill - high charge density - which typically is what reloaders strive for. A full case is basically self tamping. For this reason neck tension is particularly critical when loading. The primer will generate enough pressure to start the bullet on its way before case pressure rises sufficiently to initiate complete powder ignition. This is why I suggest crimping, although that is merely a crutch for inconsistent or inadequate case neck tension.

Some folk recommend using "hotter" primers, like the Winchester RL, or even magnum primers. These may work, but as I pointed out, they are only a crutch, not a solution.
I should have realized a narrower bullet needs a narrower neck. DUH... I have a smaller expander that came with the die set (rcbs) which measures .308 on the dial. and I do have a lee crimper, but i'll try the smaller expander first. thanks
 

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Why must this bullet be crimped in ? I know that is the special sauce of what the Finns did for military ammo....but crimping in bullets is not necessary for bolt rifles in civilian use.

Leon, are you taking Pete needlessly into crimping ...I know you like to do it but tell us why it has to be , absolutely has to be done on this bullet. I have some D166 and they do fine w/o a crimp.
 

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Discussion Starter · #10 ·
Why must this bullet be crimped in ? I know that is the special sauce of what the Finns did for military ammo....but crimping in bullets is not necessary for bolt rifles in civilian use.

Leon, are you taking Pete needlessly into crimping ...I know you like to do it but tell us why it has to be , absolutely has to be done on this bullet. I have some D166 and they do fine w/o a crimp.
I understood leon's advice to mean that a crimp is something to do if I can't do what I should do, which is getting the right neck tension. I do not take lightly the advice of a cult leader.
 

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Pete,

Load your ammo, see how it shoots (accuracy) and determine if you need to get a crimp die and use it. You can feel bullet as it seats and if it just slips in....with little resistance, thats a problem round . Problem for accuracy. I am sure you load 10 rounds , you'll get the feel.

In a perfect world if your case necks have neck walls of same thickness, the crimp will set neck tension universally the same. However if neck walls are not turned to same thickness...your crimp die will certainly crimp but neck tension will be all over the map.

So lets go back to the sizing die and its expander ball....if that is (as an example) .307 and your bullet is .308 then you should have sufficient neck tension and be okay . So if you are loading .310 bullets, you need a .309 expander ball. SOme would say .308 for .310 bullets and the easy way to end that argument is ...do you shave copper off bullet as you seat...if you see that, you ball is too tight/ small.

Having said all of that , I looked at your first input and the concern is carbon on rims..easy enough to fix, try to back out your sizing die 1/16 or 1/8 of a turn, size a few cases, seat bullets and make a dummy round and see if they chamber in rifle. (obviously no primer or powder in case).

Your chamber may be a tad over sized. Adjusting sizing die will fix that issue for the brass to fit better. I had a rather largely oversized chamber and adjusting die so sizing of brass fit the chamber ended all sooty cases or carbon anywhere and accuracy shot up to what I expected of the rifle.
 

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I understood leon's advice to mean that a crimp is something to do if I can't do what I should do, which is getting the right neck tension. I do not take lightly the advice of a cult leader.
Exactly. If you have a .308" expander for your RCBS die, use it and you should get adequate neck tension. You could load a test batch with and without a crimp and compare the results. Oh, I highly recommend removing the decapper pin from your resizer die. Use instead e.g. a Lee universal decapper. One off-center flash hole will bend the spindle and make problems with run out (concentricity.)

Comrade Milprileb has been known to use an expander that is 0.002" undersized, or even more. This will work with a boat tail bullet, since the taper will act as a secondary expander. But with a flat base bullet, undersizing the case neck too much will result in "trauma" when you seat the bullet. The Lapua D166, and its kindred 185 gr .308 D46, have the unique stepped boat tail, and it will act like a flat base bullet if the case neck has not been expanded enough.
 

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Pete, it is true at one time I was using an expander ball .002 smaller than the bullet and that was because my brass necks had spring back after sizing and my neck tension was varying with each round. I no longer size necks this small. I now anneal brass, have brass necks that hold the set when necks are resized.

Let us know if you fix the carbon on rims or not.
 

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Prairie State Pete

I am the M39 owner of which Leon references. I gave him and Milprileb headaches for quite some time helping me through my "issue". Follow the advice above.
 

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The Lapua D166 in the Finn M39 poses a problem for reloading for this reason: the throat depth of the chamber is too long for the bullet.

In the ideal reloading situation, the primer fires, generating hot gas that raises pressure inside the case even before powder ignition. This pressure is more than enough to start moving the bullet. In a "normal" rifle, the throat's leade - where the rifling begins - is close enough that the bullet encounters it, and is resisted in further forward movement. At this point the combustion of the powder inside the case can generate sufficient pressure to begin expanding the cartridge case to conform to the dimensions of the chamber. So when the case has expanded and there is no more way for the gas pressure to expand, the bullet is driven into the rifling and on its way down the barrel.

With the D166, the major diameter rear part of the bullet is clear of the case mouth before the ogive runs into the leade and encounters resistance. So whatever gas pressure that has built up inside the case after the primer functions can vent out of the case neck. This is what shows up as soot on the case.

So the critical detail in reloading the D166 is neck tension. It has to constrain the bullet's movement inside the case neck long enough for the primer's flash to get the powder burning and pressure built up to expand the case before the D166 "uncorks" and allows the pressure inside the case to relieve.

The above scenario is true for all calibers, but in many - most? - cases the bullet is still plugging the case neck when it encounters resistance from the leade. So in this scenario inadequate or inconsistent neck tension will be harder to diagnose since the tell-tale sooty case evidence is not present.
 

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The Lapua D166 in the Finn M39 poses a problem for reloading for this reason: the throat depth of the chamber is too long for the bullet. .

So the critical detail in reloading the D166 is neck tension. It has to constrain the bullet's movement inside the case neck long enough for the primer's flash to get the powder burning and pressure built up to expand the case before the D166 "uncorks" and allows the pressure inside the case to relieve.

The above scenario is true for all calibers, but in many - most? - cases the bullet is still plugging the case neck when it encounters resistance from the leade. So in this scenario inadequate or inconsistent neck tension will be harder to diagnose since the tell-tale sooty case evidence is not present.
Yes and maybe NO. If your case is sized by your Full Length sizing die to fit in a normal size chamber, what Leon says here is on the money and a "proper crimp" will do the mission. If your chamber is a bit over sized, then you may need to crimp (per Leon) but also back out your sizing die a tad so your sized brass is not so aggressively sized and is a bit larger so it can expand and seal in chamber once round is fired. Just back out die 1/8 a turn , size a few cases and see if the fit. If not, back out 1/16 a turn and test. If they do...at 1/8 or 1/16 then you do have a over sized chamber and need to size cases differently for this rifle.

That said, if chamber is oversized and brass is now sized to fit it...that may solve the sooty issue or still need the crimp per Leon's thread.

I say all the above because if sooty cases still persist after crimping D166 bullets...there is something else going on and the solution is not more and more crimp. There is a limit to crimping..you do not want to deform the bullet.

Once you have solved the soot issue , then you can ponder the immense dynamics of case neck tension but only if you are chasing accuracy at longer ranges ..400 yd and above.

You can feel the resistance of bullets as they are seated in your brass. If you notice the feel fluctuates..then the neck tension of case necks is different. Does not mean you did anything wrong in sizing, it means the inside diameter of the necks is fluctuating. How to get them all the same ?

Pete: you get to the point of inside neck diameters and how to cope with that...ask that question to me in a PM and I'll tell you what I did . Right now, just focus on soot and getting optimum accuracy with D166 bullets.
 

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Discussion Starter · #19 ·
Pete, I did not see you mention what rifle you shoot these loads in?

Daniel39
it's a 1968 m39.

to milprileb, it is 3.147 from the bolt face to when a d166 touches the lands. I bet the cases could be a tad longer. could a longer case affect accuracy? if so, I will experiment even if .308 expander solves soot problem.
 

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it's a 1968 m39.

to milprileb, it is 3.147 from the bolt face to when a d166 touches the lands. I bet the cases could be a tad longer. could a longer case affect accuracy? if so, I will experiment even if .308 expander solves soot problem.
How did you measure? I have a Hornady OAL gauge and it has saved a lot of time, and ammo, in setting OAL for my Swedish Mauser and Swiss reloads, but it is useless for the M39 because the bullet is almost falling out of the case when the D166's ogive meets the leade.

As Milprileb mentioned, you can adjust your die to minimize the amount of resizing, but that will do nothing to move the seated bullet any closer to the leade. The M39 is a "long jump" athlete compared with its contemporaries, which can be loaded so the freebore "jump" is in the 0.010"~0.020" range.

Freebore "jump" is a critical factor in reloading and the accuracy we hope to achieve. But it can be illusive and counterintuitive. To illustrate, I loaded a batch of 220 gr RN bullets for my KRAG with the OAL as published in the Lyman 49th Ed manual. I then used the OAL determined by measurement with the Hornady gauge. This round was too long to fit in the magazine so it had to be single loaded. I then made a third test batch, with the OAL set to the longest possible that would still fit the magazine.

The ammo with the manual-spec OAL and the ammo with the measured-to-the-leade OAL shot with the same sized groups. The intermediate length OAL rounds, between the longer and the shorter OAL, shot poorly, with wide grouping.
 
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